MOS Device Having Source and Drain Regions With Embedded Germanium-Containing Diffusion Barrier

摘要

An integrated circuit structure includes a gate stack over a semiconductor substrate, and an opening extending into the semiconductor substrate, wherein the opening is adjacent to the gate stack. A first silicon germanium region is in the opening, wherein the first silicon germanium region has a first germanium percentage. A second silicon germanium region is over the first silicon germanium region, wherein the second silicon germanium region has a second germanium percentage higher than the first germanium percentage. A third silicon germanium region is over the second silicon germanium region, wherein the third silicon germanium region has a third germanium percentage lower than the second germanium percentage.

主权项

1. A method comprising:
forming a gate stack over a semiconductor substrate; forming an opening extending into the semiconductor substrate, wherein the opening is on a side of the gate stack; performing a first epitaxy to grow a first silicon germanium layer in the opening, wherein the first silicon germanium layer has a first germanium percentage; performing a second epitaxy to grow a second silicon germanium layer over the first silicon germanium layer, wherein the second silicon germanium layer has a second germanium percentage higher than the first germanium percentage; and performing a third epitaxy to grow a third silicon germanium layer over the second silicon germanium layer, wherein the third silicon germanium layer has a third germanium percentage lower than the second germanium percentage, each of the first and the third silicon germanium layers having a continuously increased germanium percentage, with higher portions of each of the first and the third silicon germanium layers having germanium percentages higher than germanium percentages in respective lower portions.